Glowing fingerprints to highlight criminals

Fingerprinting powders are still the go-to tool for investigators, both real and fictional. However, instead of oils, some fingerprints only leave a residue of amino acids and other compounds that fingerprinting powder doesn't adhere to very well. A new technique developed at Australia's CSIRO not only reveals fingerprints in cases where dusting won't, but makes them glow under UV light.

After his house was broken into, CSIRO materials scientist Dr Kang Liang saw first hand how important fingerprinting is for law enforcement agencies. Dusting for prints is still the most common technique used by investigators, but there are a number of different methods to collect latent (hidden) fingerprints from a crime scene.

Superglue fuming or the use of chemical reagents are widely used when dusting fails, but these can be time consuming or will usually require the object being examined to be sent to a lab, which isn't always possible. Liang wondered if new materials might provide another alternative that could overcome the shortcomings of current techniques.

He turned to metal-organic framework (MOF) crystals that, when applied to surfaces in a drop of liquid, rapidly bind to fingerprint residue, including proteins, peptides, fatty acids and salts. In around 30 seconds, this results in an ultrathin coating that forms an exact copy of the fingerprint and glows under UV light, enabling high resolution images to be easily captured for analysis. Different colored fingerprints are also possible by altering the chemistry of the solution.

"Because it’s done on the spot, a digital device could be used at the scene to capture images of the glowing prints to run through the database in real time," says Dr Liang, who added, "because it works at a molecular level it’s very precise and lowers the risk of damaging the print."

Having successfully tested it on nonporous surfaces, such as window and wine glass, metal blades and plastic light switches, the CSIRO says the technique offers numerous advantages for forensics teams. These include the speed with which the fingerprints are revealed, their brightness under UV light, the fact no dust or fumes are produced by the process, and the low cost of the MOF crystals.

In addition to fingerprinting, the CSIRO believes the technique could find applications in other fields, such as the development of biomedical devices and drug delivery. However, for the time being it is the forensics potential that is to be pursued, with the organization looking to partner with law enforcement agencies in applying the technique.

The team's paper describing the new fingerprinting method appears in the journal Advanced Materials and Dr. Liang outlines the technique in the video below.